1. Field of the Invention
The present invention relates to an absolute coordinate encoder for positional control devices such as robots, automatic positioning device, etc., and more particularly, to an electronic absolute coordinate encoder which can continuously monitor and detect the position of the positioning system even in case of power interruption.
2. Description of the Prior Arts
Conventional positional control devices utilizing a driving motor are well known. In such positional control devices, a microcomputer employed as the system controller thereof compares the current position data detected from the positioning system with the destination position data and drives the motor to accelerate or to decelerate based on the difference between the current position and the destination position in order to perform the position control.
However, these conventional positional control devices suffer from the disadvantage that if the power supply is cut off during the position control, the current position data of the positioning system which has been counted by a digital position detector is cleared too. Thus, when the power supply is applied again, the positional control system cannot identify the coordinate of the current position where the positioning system stopped and thus must perform search operation to find the original position of the positioning system before the main position control.
Recently, positional control devices which utilize an absolute coordinate encoder having a rotational disk which is mounted on the shaft of the motor to sense the current position of the positioning system have also been proposed and developed to the initial state of practical use. However, due to the limitation of scaledown of the disk, such devices also have drawbacks that such an absolute coordinate encoder cannot be employed to the devices using a small motor but can be employed only to the devices using a motor of about 300 W or more.